Thanks for the suggestions and info. A side note: It’s interesting because even on my main domain (typierce.com) I still can’t use my custom email "email@example.com" with Formloom 3 as the To/From email address. Nothing gets sent or delivered even though it’s the same email extension as my domain. And this has been a long standing issue even before I switched to Midphase. I’m at least able to use my @gmail.com email address to send and receive with Formloom 3, but not my custom email address even though it’s on the same domain.
All that to say, I don’t think the To/From email field in the Booking stack has to be To/From a custom email with the same extension as the domain that it’s on. I would assume it’d work with any email address.